Motor vehicles, particularly large over-the-road trucks and other wheeled equipment used in mining and other heavy industrial applications, utilize various extremely large and heavy mechanical components. While such components (i.e., engines, transmissions, differentials, etc.) generally tend to be extremely durable due to their massive construction, they nevertheless must be removed from the vehicle from time to time for maintenance or repair.
The handling of such components requires mechanical or power assistance, duet the weight and bulk of such articles. While some of these components lend themselves to lifting or hoisting with mechanical or hydraulic hoists (e.g., many engines provide for the bolting lifting loops or eyes to the block or head), other components an be difficult to move and maneuver, due to the lack of provision of lifting attachment points. While a lifting attachment may be secured to some points (e.g., existing bolt holes or the like) of some of these components, the attachment point is generally not on the center of gravity of the component, making it difficult to maneuver into the desired position.
In the case of axle differentials in heavy duty vehicles and equipment, the standard means used to lift and maneuver such devices is to weld a lifting eye or loop (e.g., a chain link) to the exterior of the case over the approximate center of gravity thereof, to provide for the attachment of a sling or hoist thereto. While such a procedure enables the differential to be lifted, several disadvantages are apparent using such a technique. First of all, the localized melting of the metal of the case during the welding operation can weaken the case at that point, or at least introduce localized thermal stress in the case at that point, possibly leading to a crack or fracture of the case at some later time. Secondly, since there are numerous different models and types of differentials in use, it can be difficult to install the lifting eye over the precise center of gravity of the differential, unless the mechanic is highly experienced and knows the precise characteristics of the various differentials with which he is working. Finally the welding of a link to the differential case is a relatively time consuming operation, in that the welding equipment must be obtained, the weld made, and the completed weld allowed to cool somewhat before further handling takes place. The relatively thick metal of the case requires a relatively large welding tip (for gas welding) or high amperage (for electric arc), resulting in a large amount of heat released.
Accordingly, the need arises for a differential hoist fixture providing for attachment to an existing differential case without need for modification thereof. The fixture must provide means for positive clamping to the case to preclude slippage therefrom, and must also provide for adjustment to allow for different centers of gravity of different types of differentials.